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  1. #include<bits/stdc++.h>
  2. using namespace::std;
  3.  
  4. const long long inf = 1e18;
  5.  
  6. struct node{
  7. 	long long ans;
  8. 	long long total;
  9. 	long long prefix;
  10. 	long long suffix;
  11. 	node(){
  12. 		ans = prefix = suffix = -inf;
  13. 		total = 0;
  14. 	}
  15. 	node(int x){
  16. 		ans = total = prefix = suffix = x;
  17. 	}
  18.  
  19. 	node operator + (const node R){
  20. 		node q;
  21. 		q.ans = max(ans, max(R.ans, suffix + R.prefix));
  22. 		q.suffix = max(R.suffix, R.total + suffix);
  23. 		q.prefix = max(prefix, total + R.prefix);
  24. 		q.total = total + R.total;
  25. 		return q;
  26. 	}
  27. };
  28.  
  29. template<class T>
  30. struct SegTree{
  31. 	int n;
  32. 	vector<T> st;
  33.  
  34. 	void set(vector<T> &a){
  35. 		n = a.size();
  36. 		st.assign(4 * n, 0);
  37. 		for(int i = 0; i < n; i++) update(i, a[i]);
  38. 	}
  39.  
  40. 	void update(int x, T y, int pos, int l, int r){
  41. 		if(l == r){
  42. 			st[pos] = y;
  43. 			return;
  44. 		}
  45. 		int mi = (l + r) / 2;
  46. 		if(x <= mi) update(x, y, 2 * pos, l, mi);
  47. 		else update(x, y, 2 * pos + 1, mi + 1, r);
  48. 		st[pos] = st[2 * pos] + st[2 * pos + 1];
  49. 	}
  50.  
  51. 	T query(int x, int y, int pos, int l, int r){
  52. 		if(y < l or r < x) return T();
  53. 		if(x <= l and r <= y) return st[pos];
  54. 		int mi = (l + r) / 2;
  55. 		return query(x, y, 2 * pos, l, mi) + query(x, y, 2 * pos + 1, mi + 1, r);
  56. 	}
  57.  
  58. 	void update(int x, T y){
  59. 		update(x, y, 1, 0, n - 1);
  60. 	}
  61.  
  62. 	T query(int x, int y){
  63. 		return query(x, y, 1, 0, n - 1);
  64. 	}
  65. };
  66.  
  67. int main(){
  68. 	int n, q;
  69. 	scanf("%d %d", &n, &q);
  70. 	vector<node> a(n);
  71. 	for(int i = 0; i < n; i++){
  72. 		int x;
  73. 		scanf("%d", &x);
  74. 		a[i] = node(x);
  75. 	}
  76. 	SegTree<node> st;
  77. 	st.set(a);
  78. 	printf("%lld\n", max(0ll, st.st[1].ans));
  79. 	while(q--){
  80. 		int i, v;
  81. 		scanf("%d %d", &i, &v);
  82. 		st.update(i, node(v));
  83. 		printf("%lld\n", max(0ll, st.st[1].ans));
  84. 	}
  85. 	return 0;
  86. }
Success #stdin #stdout 0.01s 5424KB
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stdin
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5 2
5 -4 4 3 -5
4 3
3 -1
stdout
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8
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7
https://ideone.com/cIePkT
language:
C++14 (gcc 8.3)
created:
1 year ago
visibility:
public

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